Page 24 - Concise Pathology for Exam Preparation ( PDFDrive )

1 Cell Injury and Cell Death 9

Q. Differentiate between metaplasia and dysplasia.

Ans. Differences between metaplasia and dysplasia are shown in Table 1.1.

TABLE 1.1. Differences between metaplasia and dysplasia
Features Metaplasia Dysplasia
Definition Replacement of one adult epithelial or Disordered cellular development charac-
mesenchymal cell type by another terized by
(a) Loss of orientation of cells with re-
spect to one another
(b) Lack of uniformity of individual
cells
Types Squamous, columnar (epithelial) and Epithelial only
osseous, cartilaginous (mesenchymal)
Cellular pleomorphism Mature cellular development; no pleo- Disordered cellular development due to
morphism aberrant/delayed maturation or differen-
tiation; pleomorphism present
Natural history Reversible on withdrawal of stimulus May regress on withdrawal of inciting
stimulus or progress to higher grades of
dysplasia or carcinoma in situ

Q. Write briefly on aetiopathogenesis and biochemical basis of cell
injury.
Ans. Sublethal or chronic injurious stimuli can cause ‘reversible and irreversible cell
injury’.

Causes of Cell Injury
• Genetic
• Development defects (errors in morphogenesis)
• Cytogenetic defects (chromosomal abnormalities)
• Single gene defects (Mendelian disorders)
• Multifactorial inheritance disorders
• Acquired
• Hypoxia (ischaemia, anemia, carbon monoxide poisoning, cardiorespiratory failure).
• Physical agents (trauma, thermal injury, radiation, electric shock, pressure
changes)
• Chemical agents/drugs (heavy metals, acids/alkalies, insecticides/herbicides, alcohol,
smoking)
• Microbial agents (bacteria, viruses, fungi, rickettsiae, parasites)
• Immunological agents (autoimmunity, hypersensitivity)
• Nutritional imbalance (deficiency of protein, calories, trace elements, vitamins, excess
cholesterol).
• Psychological factors
The cellular responses to pathological stimuli depend on
(a) Type, duration and severity of the injury.
(b) Type, status and adaptability of the target cell.
The most important targets of injurious stimuli are
(a) Aerobic respiration (involving mitochondrial oxidative phosphorylation and production
of ATP)
(b) Cell membrane
(c) Protein synthesis
(d) Cytoskeleton
(e) Genetic apparatus

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